The invention relates to a process of exposing a photosensitive member.
A variety of processes have been proposed to effect a slitwise exposure of a photosensitive member moving in a given direction, by projecting an optical image of a stationary original onto the photosensitive member through exposure optics including movable part. These processes are in practical use in electrophotographic copying machines or apparatus for preparing masters in electrostatic printing arrangements.
In one process of exposing a photosensitive member which is well known and is extensively used, exposure optics including movable part is employed to effect a slitwise exposure of a photosensitive member, moving in a given direction, at a home location within the space of the arrangement by causing a movement of the movable part. In this arrangement, the time required for the movable part to return to its start position upon completion of the exposure which took place through the movement of the movable part cannot be utilized for initiating another exposure. Consequently, where a succession of copying operations are desired, there is produced a surface region on the photosensitive member which is located intermediate the trailing end of a first electrostatic latent image and the leading end of a second or next latent image and where no latent image can be formed. This presents a problem from the standpoint of an effective utilization of the photosensitive surface.
There is proposed an exposure process which permits an exposure of the photosensitive member during the returning movement of the movable part through a sophisticated design of the exposure optics, but which requires a complex arrangement and an increased cost. In addition, the latent images which are consecutively formed are oriented in opposite directions from adjacent ones, requiring a re-orientation of the resulting copies, which is troublesome.
A succession of electrostatic latent images can be formed in a manner such that the adjacent images are continuous from adjacent ones, by effecting exposure while maintaining the photosensitive member at a pause. However, an intermittent movement of the photosensitive member is necessary, requiring a complicated sequence control of the process. In addition, the movement of the photosensitive member is frequently interrupted because of the exposure, resulting in a reduced average speed of movement of the photosensitive member, which generally causes a reduction in the copying efficiency.